Noise Reduction with Sub-Channel Sorting for OFDM-CDM

In this paper, we consider an Orthogonal Frequency Division Multiplexing-Code Division Multiplexing (OFDM-CDM) system. The noise reduction method based on Least Squares (LS) is introduced into the OFDM-CDM receiver to improve the signal-to-noise ratio (SNR), while the system does not work under full load. In this paper, Walsh code is considered to be used in CDM module. The relationship between the spreading codes and the variance of the noise after noise reduction is investigated. Based on this relationship, a simple noise reduction after channel frequency response (CFR) sorting is proposed to improve the Bit Error Rate (BER) performance of system further. Simulation results suggest that good performance can be achieved with proposed scheme.